I would think a little out of the box, in this case.

Write to AA and/or DL asking if they can status match your AC status (whatever it is). At least one of them will match (I know that AA does it regularly).

Once you have the other airlines' status (from different Alliance) UA will consider you for (usually) Gold.

If you plan to use this route, I suggest you do this immediately, as by the year end, you will not have this option any more as the new spending requirement kicks in next year onward.